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Effect of nutrient limitation on the Mediterranean flour moth, Ephestia kuehniella Zeller : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Entomology at Massey University, Palmerston North, New Zealand

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Abstract

The Mediterranean flour moth, Ephestia kuehniella is a cosmopolitan pest of stored
products that now has wide distribution in flour/feed mills in New Zealand.
Understanding how individual behaviour and life‐history strategies evolve in
response to environmental variation will help predict the population dynamics and
allow us to develop environmentally safe pest control measures.
This study investigated effects of food shortage and the responses this stimulated
in E. kuehniella. I artificially created food stress environment by rearing E.
kuehniella larvae at five different population densities of 50, 100, 200, 400 & 800
on a constant amount of diet (50 g). Population density had a detrimental effect on
E. kuehniella fitness. At higher population density (800) due to food shortage larval
period was prolonged, percent survival and pupal mass of both sexes decreased.
Poor nutrition during the larval stage also effected adult morphology and
reproductive output. Female fecundity decreased with increased population
density. Females that developed at high population density (800) emerged with
small head, thorax and forewing, but food stressed females developed large
abdomens relative to their body mass. There were no significant changes in female
ovipositor length in response to nutrient limitation indicating that under poor
environmental conditions females allocate more resources to reproduction and in
particular to traits that influence offspring. In males, head and thorax width
decreased with increased population density. Males at higher population density
had large forewings relative to their body mass, possibly to aid movement to new
habitats. Genital traits were insensitive to food shortage resulting from crowding.
Although males at population densities of 400 & 800 produced fewer eupyrene
sperm they had similar mating frequency and transferred similar numbers of
apyrene sperm indicating that male development responds to juvenile
environment. Males and females use visual and chemical cues to assess quality of
potential mates during mate selection and prefer individuals that developed at
high population density (800) compared to low population density (200) when
their weights were matched, probably to obtain direct and indirect genetic
benefits. Ephestia kuehniella obtains indirect genetic benefits through mate choice
decisions. Body size has a heritable component and large parents produce large
sons and daughters. Mother body mass influences offspring growth rate and
daughter developmental period is shortened with increase in mother body mass
but no such effect was observed on son developmental period indicating a nongenetic
maternal effects. On the other hand, fathers do not have a notable influence
on offspring growth rate and as a result the offspring of large fathers took longer to
develop. Similarly, sons and daughters of polyandrous and cross culture females
were heavier and polyandry increased female fitness especially in stressful
conditions.